To solve problems where we already know the value of the variable, all we must do is substitute in that value. In this case, we will substitute in 6.3 for every instance of x.
Also, the +(- ) is a complicated way of writing "-," so we will refer to the problem as -x-7.5.
=-x-7.5
=-6.3-7.5
=-13.8
Using the math above, we can see that it equals -13.8.
